Method for forming a barrier layer

ABSTRACT

Methods and devices are disclosed utilizing a silicon-containing barrier layer. A method of forming a barrier layer on a semiconductor device is disclosed. A semiconductor device is provided. A silicon-containing material is deposited on the semiconductor device. The silicon-containing material is processed in a reactive ambient. The barrier layer can be made primarily oxide, primarily nitride or both by the reactive ambient selected. A semiconductor device is disclosed. The semiconductor device includes a substrate, a gate oxide, a silicon-containing barrier layer and a gate electrode. The gate oxide is formed over the substrate. The silicon-containing barrier layer is formed over the gate oxide by causing silicon atoms of a precursor layer react with a reactive agent. The gate electrode is formed over the silicon-containing barrier layer. Other embodiments utilizing a barrier layer are disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.09/653,639, filed Aug. 31, 2000.

FIELD OF THE INVENTION

The present invention relates to the field of semiconductors and, moreparticularly, to an improved barrier layer for increasing semiconductorperformance.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is related to commonly assigned U.S. patent applicationSer. Nos.: 09/653,096, METHOD FOR FORMING A DIELECTRIC LAYER TO INCREASESEMICONDUCTOR DEVICE PERFORMANCE, filed Aug. 31, 2000, by Powell et al.and 09/653,298, METHOD FOR FORMING A DIELECTRIC LAYER AT A LOWTEMPERATURE, filed Aug. 31, 2000, by Mercaldi et al., the disclosures ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

There is a constant demand for semiconductor devices of a reduced size.The performance of semiconductor capacitors, transistors, electrodelayers and the like in semiconductor devices becomes more critical asdevice size decreases. Accordingly, processes that result in increaseddevice performance are critical to improved semiconductor devicefabrication. For example, capacitor and transistor performance can beimproved by limiting diffusion of oxygen to transistor active areas orcapacitor electrodes.

Barrier layers are generally used in circuitry and semiconductor devicesto enhance performance by reducing diffusion, migration and reaction.Accordingly, there is a continuing need for improved barrier layertechnology directed at improving semiconductor device performance.

SUMMARY OF THE INVENTION

This need is met by the present invention wherein a method of forming abarrier layer on a semiconductor device is disclosed. According to oneembodiment of the present invention, a semiconductor device is provided.A silicon-containing material is deposited on the semiconductor device.The silicon-containing material is processed in a reactive ambient.

According to another embodiment of the present invention, asemiconductor device is disclosed. The semiconductor device includes asubstrate, a gate oxide, a silicon-containing barrier layer and a gateelectrode. The gate oxide is formed over the substrate. Thesilicon-containing barrier layer is formed over the gate oxide. The gateelectrode is formed over the silicon-containing barrier layer.

Other methods and devices are disclosed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following detailed description of the present invention can be bestunderstood when read in conjunction with the accompanying drawings,where like structure is indicated with like reference numerals.

FIG. 1A illustrates a semiconductor device using a barrier layeraccording to one embodiment of the present invention.

FIG. 1B illustrates a transistor semiconductor device utilizing abarrier layer according to one embodiment of the present invention.

FIG. 2A is a flowchart of a method for fabricating a barrier layeraccording to another embodiment of the present invention.

FIG. 2B illustrates exemplary thickness measurements of the barrierlayer using the method of FIG. 2A.

FIG. 3 illustrates capacitance characteristics of a semiconductor deviceutilizing a barrier layer according to another embodiment of the presentinvention.

FIG. 4 illustrates a barrier layer according to another embodiment ofthe present invention.

FIG. 5 is an illustration of a computer system for use with embodimentsof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1A illustrates a semiconductor device 108 using a barrier layer 102according to one embodiment of the present invention. The semiconductordevice 108 is merely illustrated schematically in FIG. 1 and istypically fabricated proximate to a substrate 101. More specifically,the semiconductor device 108 may be formed in, on or over the substrate101. For the purposes of defining and describing the present invention,it is noted that a semiconductor device 108 may comprise a transistor,capacitor, electrode, insulator or any of a variety of componentscommonly utilized in semiconductor structures. The substrate 101 maycomprise one or more semiconductor layers or semiconductor structureswhich may define portions of the semiconductor device 108. The barrierlayer 102 is formed over the semiconductor device 108. Generally, thebarrier layer 102 is formed by depositing one or more precursormaterials from a silane or silazane source and converting the depositedmaterials into the barrier layer 102 by subsequent processing of thedeposited materials. The subsequent processing of the depositedmaterials involves subjecting the deposited materials to a reactiveagent, such as an oxidizing or nitridizing species, which will reactwith silicon in the deposited materials. The barrier layer 102 reducesor prevents diffusion or migration of dopants into and out of thesemiconductor device 108 and reaction or oxidation of the materialsforming the semiconductor device 108.

FIG. 1B illustrates a transistor semiconductor device 109 utilizing abarrier layer 102 according to another embodiment of the presentinvention. A source 105 is formed in a substrate 101. A drain 106 isformed in the substrate 101. A gate oxide layer 104 is formed over thesubstrate 101 from the source 105 to the drain 106. A barrier layer 102is formed over the gate oxide layer 104. An electrode or gate electrode103 is formed over the barrier layer 102. The source 105, the drain 106,the substrate 101, the gate oxide layer 104 and the gate electrode 103may be provided in accordance with convention techniques ofsemiconductor fabrication.

The barrier layer 102 is fabricated by vapor depositing one or moreselected materials or precursors from a silicon source and subsequentlyprocessing those materials or precursors. The silicon source may be asilazane or a silane source such as hexamethyldisilazane (HMDS). Othersilicon sources which may be used are tetramethyldisilazane,octamethylcyclotetrasilazine, hexamethylcyclotrisilazine,diethylaminotrimethylsilane or dimethylaminotrimethylsilane. Theselected material is processed in a reactive ambient to create a finaldesirable silicon-containing barrier layer. Reactive ambients includeoxygenating or nitridating species which will react with silicon to formthe silicon-containing barrier layer. Some reactive ambients are NH₃,N₂, O₂, O₃, NO and the like. The resulting silicon-containing barrierlayer is the barrier layer 102 and may comprise a layer that isprimarily nitride, primarily oxide or an oxynitride depending on thereactive ambient selected.

The barrier layer 102 prevents dopants, such as boron, in the gateelectrode 103 from diffusing into the gate oxide layer 104, the source105 and the drain 106. The barrier layer 102 also prevents reactionsbetween the gate electrode 103 and the gate oxide layer 104, preventsmigration of dopants from the gate electrode 103 to other areas of thesemiconductor device, prevents oxidation of the gate electrode 103 andprevents the formation of suicides on the gate electrode.

FIG. 2A illustrates a method for fabricating a barrier layer accordingto one embodiment of the present invention. A wafer or substrate isprovided at block 201. The wafer or substrate is cleaned usinghydrofluoric acid (HF) at block 202. A silicon-containing material isvapor deposited onto the surface of the wafer at block 203 from asilicon source. The silicon-containing material is treated or processedusing rapid thermal nitridation (RTN) in an NH₃ ambient at block 204resulting in creation of the barrier layer. The temperature, anneal timeand processing pressure are selected to obtain desired barrier layercharacteristics. A wet oxidation layer is formed over the barrier layerat block 205.

FIG. 2B illustrates thickness measurements of the barrier layer and wetoxidation layer created using the method of FIG. 2A using variousprocessing conditions. In this figure, the wet oxidation has a thicknessof 300 Å. For this particular example, FIG. 2B illustrates that asuitable barrier layer may be formed at about 450 Torr and 850° C., overa processing time of 60 seconds with minimal oxidation of the underlyingsilicon substrate. It is noted that the 850° C. processing temperatureis lower than the processing temperature (typically 950° C.) used tocreate barrier layers using conventional methods. In addition, the 60seconds processing time is lower that the processing time used to createbarrier layers using conventional methods (typically 45 minutes).However, the processing time can be longer without a detrimental affectif silane or silazane silicon sources are used because they are selflimiting.

Generally, conventional barrier layers are processed using temperatureranges of 700° C. to 1050° C., processing time of 10 seconds to 60minutes, and processing pressure of 760 torr. Whereas, the barrier layerof the present invention is typically processed using temperature rangesof 500° C. to 900° C., processing time of 30 seconds to 5 minutes, andprocessing pressure of 450 torr. It is contemplated that variations tothese ranges may also result in suitable barrier layer formation.

Referring to FIGS. 1B and 3, FIG. 3 illustrates the capacitancecharacteristics of a semiconductor device 109 utilizing a barrier layer102 according to the present invention. The capacitance characteristicsof a device with a conventional barrier layer with a N+ PH₃ dopedpolysilicon gate electrode are illustrated at 301. Line 302 illustratesthe capacitance characteristics of a device with a conventional barrierlayer and a BF₂ doped polysilicon gate electrode. Line 303 shows thecapacitance characteristics of a barrier layer 102 created by vapordepositing HMDS with a N+ PH₃ doped polysilicon gate electrode 103. Line304 shows the capacitance characteristics of a device with a barrierlayer 102 created by vapor depositing HMDS with a BF₂ doped polysilicongate electrode. Comparing the capacitance values of lines 301 and 302with lines 303 and 304, it is noted that negative bias capacitance isenhanced by the present invention. The barrier layers used in lines 303and 304 were processed using NH₃ and O₂.

In addition, line 302 shows how the conventional barrier layer suffersboron diffusion into the gate and active areas (note the shift inthreshold voltage at 306). Line 307 shows that the measured workfunction, associated with the vapor deposited HMDS barrier layers oflines 303 and 304 match theoretical values.

FIG. 4 illustrates use of a barrier layer 402 according to anotherembodiment of the present invention. The barrier layer 402 is locatedbetween a dielectric 403 and a electrode 401. The barrier layer 402 iscreated by depositing a silicon-containing material (from silazane orsilane type silicon sources). The layer is then post-processed in areactive ambient. The dielectric 403 is of a material susceptible tooxygen migration such as Ta₂O₅. The electrode is of a material such asP—Si, SiGe, a metal, or any other electrode material suitable for use insemiconductor based charge storage devices.

FIG. 5 is an illustration of a computer system 512 that can use and beused with embodiments of the present invention. As will be appreciatedby those skilled in the art, the computer system 512 would include ROM514, mass memory 516, peripheral devices 518, and I/O devices 520 incommunication with a microprocessor 522 via a data bus 524 or anothersuitable data communication path. The mass memory 516 can includesilicon-containing barrier layers in, for example, transistor structuresor charge storage structures. These devices can be fabricated accordingwith the various embodiments of the present invention.

For the purposes of describing and defining the present invention,formation of a material “on” a substrate or layer refers to formation incontact with a surface of the substrate or layer. Formation “over” asubstrate or layer refers to formation either above or in contact with asurface of the substrate.

As stated earlier, barrier layers fabricated using the present inventioncan be used for a variety of purposes. Some examples follow, butembodiments of the present invention are not limited to these. A barrierlayer can be formed on top of metals to prevent oxidation of metals. Abarrier layer can be placed between metals and silicon containingmaterials to prevent agglomeration, the formation of silicides. Abarrier layer can be used in a P+ or N+ gate to prevent dopant,hydrogen, or flourine in-diffusion into the gate dielectric reducingdefect density and increasing performance and reliability. A barrierlayer can be used in post gate stack and pre oxidation steps to preventoxygen in-diffusion into active areas of the transistor. A barrier layercan be used to prevent oxidation of gate electrodes with subsequentprocessing steps when using materials such as polysilicon, Si—Ge, W orother transistion metals. A barrier layer can be used with a storagedielectric, such as non-volatile random access memory, and may be usedto reduce degradation of tunnel oxide performance.

Having described the present invention in detail and by reference topreferred embodiments thereof, it will be apparent that modificationsand variations are possible without departing from the scope of thepresent invention defined in the appended claims.

What is claimed is:
 1. A method of forming a barrier layer on asemiconductor device comprising: providing a substrate including atleast one semiconductor layer; fabricating the semiconductor deviceproximate to the substrate; depositing a silicon-containing materialfrom a silicon source over at least a portion of the semiconductordevice; and processing the silicon-containing material with a reactiveagent selected to react with silicon atoms of the silicon-containingmaterial to form the barrier layer.
 2. The method of claim 1, whereinthe silicon source is a silazane.
 3. The method of claim 1, wherein thesilicon source is selected from the group comprisinghexamethyldisilazane, tetramethyldisilazane,octamethylcyclotetrasilazine, hexamethylcyclotrisilazine,diethylaminotrimethylsilane and dimethylaminotrimethylsilane.
 4. Themethod of claim 1, wherein the silicon-containing material is from asilane source.
 5. The method of claim 1, wherein the reactive agent isselected from the group comprising NH₃, N₂, O₂, O₃, N₂O, and NO.
 6. Themethod of claim 1, wherein the barrier layer is primarily nitride. 7.The method of claim 1, wherein the barrier layer is primarily oxide. 8.The method of claim 1, wherein the barrier layer is primarilyoxynitride.
 9. A method of forming a barrier layer comprising: providinga substrate including at least one semiconductor layer; fabricating afirst semiconductor device proximate to the substrate; depositing asilicon-containing material over at least a portion of the firstsemiconductor device; processing the silicon-containing material with areactive agent selected to react with silicon atoms of thesilicon-containing material to form the barrier layer; and fabricating asecond semiconductor device over the barrier layer.
 10. The method ofclaim 9, wherein the reactive agent is NH₃ and the barrier layer isprimarily nitride.
 11. A method of forming a barrier layer comprising:providing a silicon substrate including at least one semiconductorlayer; vapor depositing a silicon-containing material from a silazanesource over at least a portion of the silicon substrate; and processingthe silicon-containing material in a reactive ambient selected to reactwith silicon atoms of the silicon-containing material at a processingtemperature, a processing time and a processing pressure.
 12. The methodof claim 11, wherein vapor depositing a silicon-containing material andprocessing the silicon-containing material are repeated at least once.13. The method of claim 11, wherein the processing temperature is about850° C., the processing time is about 60 seconds and the processingpressure is about 450 Torr.
 14. A method of forming a barrier layer in asemiconductor device including a transistor structure, said transistorstructure including a source, a drain and a gate oxide layer formed overan active area between said source and drain, said method comprising:depositing a silicon-containing material over at least a portion of thetransistor structure; processing the silicon-containing material in areactive ambient to form the barrier layer; and forming a gate electrodeover the barrier layer.
 15. The method of claim 14 further comprising:doping the gate electrode with phosphor.
 16. The method of claim 14further comprising: doping the gate electrode with boron.
 17. The methodof claim 14, wherein processing the silicon-containing material in areactive ambient comprises processing the silicon-containing material inan oxidizing agent causing silicon atoms of the silicon-containingmaterial to bond with oxygen atoms of the oxidizing agent.
 18. A methodof forming a capacitor device with a barrier layer, the methodcomprising: forming an electrode over a substrate; depositing asilicon-containing material over the electrode; processing thesilicon-containing material using rapid thermal nitridation with anitridizing reactant to form the barrier layer; and forming a dielectriclayer over the barrier layer.
 19. A method of forming a barrier layercontaining no metal on a semiconductor device comprising: providing asubstrate including at least one semiconductor layer; fabricating thesemiconductor device proximate to the substrate; depositing asilicon-containing material from a silicon source over at least aportion of the semiconductor device; and processing thesilicon-containing material with a reactive agent selected to react withsilicon atoms of the silicon-containing material to form the barrierlayer containing no metal.
 20. A method of forming a barrier layercontaining no metal comprising: providing a silicon substrate includingat least one semiconductor layer; vapor depositing a silicon-containingmaterial from a silazane source over at least a portion of the siliconsubstrate; and forming the barrier layer by processing thesilicon-containing material in a reactive ambient selected to react withsilicon atoms of the silicon-containing material at a processingtemperature, a processing time and a processing pressure.
 21. A methodof forming a barrier layer containing no metal in a semiconductor deviceincluding a transistor structure, said transistor structure including asource, a drain and a gate oxide layer formed over an active areabetween said source and drain, said method comprising: depositing asilicon-containing material over at least a portion of the transistorstructure; processing the silicon-containing material in a reactiveambient to form the barrier layer containing no metal; and forming agate electrode over the barrier layer.
 22. A method of forming acapacitor device with a barrier layer containing no metal, the methodcomprising: forming an electrode over a substrate; depositing asilicon-containing material over the electrode; processing thesilicon-containing material using rapid thermal nitridation with anitridizing reactant to form the barrier layer containing no metal; andforming a dielectric layer over the barrier layer.